Quote:
Originally Posted by KamperBob
FWIW this looks steeper than 22 degrees.
I can't help but wonder about contributions from both sides feeding the rear end. Could that support a higher angle?
I also think about how much less steep is the ridge of a hip roof compared to the sides. Point being that flow vectors with some transverse component might be considered effectively shallower with their azimuth taken into account. When working in any field (electric, magnetic, etc) cosine projections into a principle plane usually offer great advantage but maybe there are cases where a fresh or even naive look reveals something previously missed. (shrug)
Cheers
KB |
This photo,I believe is of one of Ludwig Prandtl's Jaray combination form models being tested at AVA Gottingen.
It is a pseudo-Jaray
'fastback'.Here's the rub.Yes the tufts are attached well down the back but it's not a deal-breaker for us.
Here is Dr.Hucho's explanation for what is going on.It's from page 18 of chapter-1 of his second edition,and he's speaking about these forms and specifically about the Beetle and Airflow:
(the Fastback )"produced two distinct longitudinal vortices.Due to the downwash induced by these trailing vortices,the flow along the longitudinal mid-section of the car remains attached over a long path;however,a high vortex-induced drag is produced so that the total drag is higher than for true Jaray shapes."
Hucho then comments on the fact that Cd 0.6-0.8 for boxy shapes were typical of the time and the Cd 0.4-0.5 of the pseudo-Jaray still an improvement.